John,
Firstly welcome to Talk Morgan, there will be lots of information and help here for you I am sure.
Regarding your problems, I can give you plenty of advice about tyres, as I too had to research this for my +8.
If you want a good all round road tyre then the Avon ZV-5 takes a lot of beating and comes with plenty of recommendations from users , Morgan dealers, and others. I use them in 205/60 x 15.
If you are not worried about ground clearance, or the very slight increase in fuel consumption, slightly inaccurate speedo etc then there is an even better (grippier) alternative , the Toyo Proxes T1-R, but this is only available in 205/55 x 15 which is smaller diameter, hence the points above.
Regarding the age of the tyres, the accepted wisdom here in UK is that old rubber should be replaced at around 5 years. Rubber hardens with age, and although there is plenty of tread left , there may not be a lot of grip. There are those (even on this forum ;-) ) who think this advice is just the tyre companies propaganda to make us replace them more frequently, but my experience is that I have a lot more wet grip since replacing my 9 year old Yokohama A520s with Avon ZV-5s
Regarding your first point I am really not sure what the "shop" are talking about. Do others here have any idea?
Do you have alloys or wire wheels? If the latter then I suspect that they are referring to the issues around getting the wire wheel "held" on their balancing machine. Many tyre fitting depots can now only balance wheels with stud or bolt fixing, they used to have a universal tool for using with wire wheels , but most now seem to have lost both the tool and the skill of using it. Let us know where you are located and someone might know a depot in your area who can manage the job successfully.
If you have alloys I really do not know what they mean, they should be able to balance an alloy wheel on standard equipment without the need for any spacers.
